1. Field of Invention
The present invention relates to a process for manufacturing bags. Furthermore, the process aims to provide protection for the film tube rolls used in the process.
2. Description of the Prior Art
Bags are manufactured using, among others, the so-called Form, Fill and Seal Machines, referred to in the following description as FFS machines.
Such machines are disclosed in the published patents DE 199 33 486, EP 534 062, DE 44 23 964, DE 199 20478 and DE 199 36 660. The FFS machines have unwinding stations on which film tubes are stored. These unwinding stations unwind the film tubes and separate them into film tube segments. Usually in the later process steps, the film tubes are provided with bottoms, the resulting bag is filled with the filling material and the bag is sealed. The type of bag forming and filling suggested in the aforementioned published patents is also a part of the contents of this disclosure. The same applies to the provisions of the term ‘Form, Fill and Seal machines’ (FFS) and also the processes of transporting the film tubes, film segments and bags into these machines. As a rule, these machines are used to fill the bags with bulk materials.
Usually, film tubes are formed by blown film extrusion for the purpose of processing using FFS machines. The format of these film tubes (here, their periphery) is in agreement with the bag formed. This approach necessitates the relatively expensive replacement of formats in the blown film extrusion plants for the purpose of realizing different bag formats. Moreover, the formats required for the bag formation are relatively small and hence cannot be manufactured economically. Blown film extrusion plants of bigger format produce the same foil at much lesser costs per unit of area.
Therefore, experiments have been conducted many times with the purpose of first manufacturing very broad film webs by flat film extrusion or by blown film extrusion using machines of a bigger format. Here also, blown film extrusion plants were preferred primarily for cost reasons. The resulting film tubes or film webs of a big format were then processed further to flat film webs by cutting them as per the format required.
Subsequently, one of these flat film webs is folded up and joined by a longitudinal joint seam to form a film tube. A disadvantage of such usually very short film tubes is that the thick joint created by the longitudinal joint seam complicates the winding process of the film tube, since the rolled-up film tube tends to telescope, i.e. it assumes a frusticonical shape, due to the addition of the thick joints.
Even film tube segments are produced in a similar manner for the purpose of manufacturing bags of a higher quality. Thus, for instance, the manufacture of side-gusset pouches or side-gusset bags are known to prior art that are formed out of several film segments. For this purpose the edges of each of the film segments are usually sealed together. This process is carried out between sealing jaws that clamp the material to be sealed during the sealing process.
This method is used generally to manufacture film tube segments whose length corresponds to that of bags formed later. In other cases, immediately after production, the formed film tube segments are cut immediately to the length of the bags formed later and are fed individually to the bag forming, filling and sealing machines. This type of high quality of bag manufacturing is probably well-known in the pet food sector.
However, both the transportation of individual film tube segments as well as their insertion into a bag forming, filling and sealing machine is an expensive and complex process. This process is usually executed using rotary feeders or other suction devices that grasp the film tube segments individually and feed them to the bag forming machine. Such devices are expensive and prone to breakdown.